1. Field of the Invention
The present invention relates to an optical disk apparatus and a data read-out control method for reading out data, which is recorded on an optical disk, by a laser beam that is radiated from a semiconductor laser.
2. Description of the Related Art
In recent years, game application programs are recorded on optical disks and are sold. With developments of game contents, the resolution of images and the amount of image data in the game application programs have been increasing. Accordingly, the data capacity of the game application program has been increasing. In addition, the data transfer speed for reading out the game application program recorded on the optical disk has been increased.
Examples of supply media of game application programs include a CD (Compact Disk)-ROM, a DVD (Digital Versatile Disk)-ROM (single-layer, double-layer), and an HD-DVD (High Definition DVD)-ROM. The data capacity of the supply media has gradually been increasing.
There is a tendency that users of computer games enjoy the games for a longer time. Thus, the optical disk apparatus is required to have high reliability and a long lifetime, which ensure stable operations for long-time use.
In the meantime, in order to increase the data capacity of the optical disk, the data storage density of the optical disk has been increased. In addition, in order to read/write data from/on the high-storage-density optical disk, the wavelength of a laser beam, which is radiated from a semiconductor laser, has been decreased. In the case where the wavelength of the laser beam is decreased, how to enhance the reliability and lifetime is a challenging problem. On the other hand, the lifetime of the semiconductor laser depends greatly on turn-on time (power-on time). For example, the lifetime of the semiconductor laser can be increased by turning off the semiconductor laser in the idle state in which no data is read/written from/on the optical disk.
Jpn. Pat. Appln. KOKAI Publication No. 11-312357 discloses an optical disk apparatus which includes a pickup unit which reads information recorded on an optical disk by radiating a light beam on the optical disk while executing a focus servo, a tracking servo and a traverse servo; an RF circuit which extracts a focus error signal, a tracking error signal and an RF signal; spindle servo means for controlling a spindle motor for rotating the optical disk; and control means for controlling the respective parts. In this optical disk apparatus, when the working state is switched to the idle state, the loop gain for controlling the spindle motor for rotating the optical disk is switched to the setting of the idle state, thereby reducing the generation of heat and noise.
Jpn. Pat. Appln. KOKAI Publication No. 11-232656 discloses an optical disk apparatus which includes a spindle motor for rotating an optical disk; a head which reproduces a signal that is detected from the optical disk; a reproduction process circuit which processes the signal reproduced by the head; a servo circuit which executes a servo control on the basis of an error signal indicative of an error occurring due to the rotation of the optical disk; and a memory circuit which stores a waveform of the error signal. In this optical disk apparatus, when the servo circuit is restored to the normal servo operation, the servo control is restored to the position indicated by the waveform of the error signal stored in the memory circuit. Thereby, the control is stabilized without repeating the restoration process.
In the case where the lifetime of the semiconductor laser, which is used in the optical disk apparatus, is to be increased, it is thinkable to halt data read from the optical disk and to decrease the turn-on time of the semiconductor laser. However, if the semiconductor laser is turned off and the access to the optical disk is simply halted, a considerable length of time would be needed until the optical disk apparatus is restored once again to the state in which data can be read out from the optical disk apparatus, and the data transfer rate would be decreased.